Kate Bainbridge is a lively 37-year-old former schoolteacher. We are communicating in the conservatory of her parents’ home in south Cambridge. She has expressive eyes and a broad and ready smile, but she can utter only occasional single words with difficulty. She sits in a wheelchair “speaking” with the aid of a letter-board, using her left forefinger to spell out words individually.

Ten years ago, Kate went into a deep coma and was on a ventilator for several weeks. She had suffered severe brain inflammation after contracting a viral infection. When she came out of the coma, she opened her eyes and could breathe naturally, but she was unresponsive to speech and visual stimuli, and appeared to lack all conscious awareness. She was still in this condition four months after falling ill, and was later diagnosed to be in a persistent vegetative state, or PVS: in other words, persistently unaware. But the diagnosis was wrong.